Projectile fuse



May 7, 1946 J. H. CHURCH ET AL PRQJECTILE FUSE Filed Aug. 26, 1941 Joseph H Bhur|:h Y Wilire 11E -T'hih ufieau Patented May 7, 1946 JPROJECTHJEFIIS E Joseph H. Church, Austin, .ana'wnrmup. 'Thihodeau, Cleveland, Ohio Application-August 26,1941, Serial No. $08,335

(Granted under the act of March *3, 1883, as amended April 30, 1928; 370;0.=G.7-5'7 6 Claims.

The invention described herein maybe manufacturedand used by .or for .the Government for governmental purposes, without .the payment to .us of :an y royalty thereon.

This invention .relates to projectile fuses and in particular @to a new {form of safety barrier member 'for fuses.

In .the employment of .explosive projectiles it is necessary .that means be provided to positively prevent the actuation of the percussion primer prior to the discharge of'the projectile from the barrel of the weapon. In :the initial stages of the trajectory two important forces act upon the relativel movable parts within the projectile. Theforcesoftinertia .due to the linearacceleration are commonly .called setback and tend to hold :any .-free :element in its initial position in space while the projectile proper is moved forward. During this .period the projectile is also being accelerated rotationally, in some cases to rotational velocities considerably in excess of 50;0OO-R. P. -M. The proper utilization of these forces makes possible thedevelopment :of a safe and eifective fuse.

It is an object of this invention to utilize :relatively loose fibrous materials such as glass rfiber, steel wool, rock wool, textile fibers, and the like as barriers for the :protectionof :the jprimeriunits of fuses against the forces of setback and the shocks incident :to ordinary handling of the proiectile. Atthe same timeritiisproposed' -to:utilize centrifugal force to remove these barriers at some time after the projectile has been 'fired.

It is a further object of this invention to utilize -1loose:fibrous materials in fuse construction in such amanner that thefibrous-materia1functions as a spring to hold a barrier in engagement with the firing mechanism and "to form the barrier itself.

In .some classes :of fuses centrifugally operated rigid barrier "members are employed which in moving to armedpositionrelease afiringmember .or clear a passageway. Obviously in such :fuses space must be provided into which the barrier member is to be retracted. 'It is 'thereforea'further object of our invention to'provide a nonrigid "barrier .member'which can be readily applied to fuses in which space requirements will not permit the use of 'such retractlble rigid barrier members. Accordingly we have provided "a barrier member which is permanently confined at its :outer part while its "inner part moves raoutward to allow the firing mechanism to function.

The :specific nature of the inventionas "well as other objects and advantagesthereof will clearly appeargfrom .the description of preferred embodimentsasshown in the accompanying drawing in which:

Figuresrl to .4arelongitudinalsections.of portions of projectile bodies embody n modifications .of our invention.

Referring .to.Fig. .1 the nose I .of a projectile is provided with an axial bore having .a portion of reduced diameter at itsfront-endforming a rearwardly facingshOulder-B. .A .firing pin 3 seated in the axial bore is .provided with an enlarged head engaging the shoulder 5 and with .a rearwardly facing point. Holding the firing pin against its .seat is a cylinder 4 of -relatively.loose fibrous :material .havingindividual fibers of considerable zelasticity,-such as glass fiber, steel wool, rock wool, or various textile fibers. As shown in the drawing this cylinderis provided with a portion of enlarged internal diameter serving to hold the firing ;pin in centered relationship. It must be understood, however, that other means may .beprovided to hold the firing .pin in centered relation and that the primary function of the cylinder 4 is that "of a-safety barrier. Secured in the rear-end-of the-axialbore by threads orother :means is a primer capsule :2 containing a percussion priming charge and also serving to support thecylinder-L Sufiicient clearance .is provided between "the tip of the firing pin-and theprimer capsule toinsure that blows and shocks incident to the ordinary handling ,of the projectile before and during the loading operation will be absorbed by the natural resiliency of thecylinder-d without permitting the firing pin :to contact the-primer.

-As the projectileiis fired the force of setback .tending tothrow the firing pin to .the rear is like Wise absorbed in longitudinal compression and radial thickening of the barrier member. During this period of.-1inear acceleration the longitudinalcompressioncaused by setback will produce sumcient radial :thickening to overcome the tendency of centrifugal force to release the firing pin but on the cessation "of linear acceleration centrifugal force will act .alone to compact the-fibrous structure ofthe cylinder 4 into a thin hard :layer at the periphery of the cylindrical bore, The firing pin will thereafter be free to move and, on impact with .any *target, cut-out portions :of "the target :and compression of the air trapped :at the :-nose of the projectile will impeltheffiring'epin against "the primer for actuation thereof.

it will be :noted that :a barrier member has in Figure 2 there is shown a part of the point sec- 3 tion 21 of an explosive projectile, Formed about the longitudinal axis of the projectile is a-passageway 6 tapering rearwardly from a maximum diameter at the point end of theprojectile. At the termination of the passageway 6 a primer 22 of the pinless type is seated. Such a primer depends for its actuation upon either or the combination of the efiects caused by the impact of cut-out portions of the target and the heating due to the sudden compression of the air trapped in the passageway. Seated'in the passageway 6 in advance of the primer is a plug 1 of matted flexible, fibrous material such as glass fiber, rock wool, or various other flexible fibers. The plug 1 is provided with an axial hole 8 of small diameter and the. outer portion may be causedto adhere to the walls of the passageway by the application of a suitable adhesive.

During normal handling and loading of the projectile the presence of the barrier plug serves to protect the primer from any accidental blow which might cause apremature discharge thereof. v

Upon firing the. projectile in a suitable weapon the forces of setback act to force the plug into the rear end of the passageway but on the cessation of linear acceleration centrifugal force acts to compact the plug about the periphery of the passageway and enlarge the hole 8 to the extent required to allow direct impact upon the primer. A component of centrifugal force due to the tapered wall of the passageway will act to move the plug forward along the axis of the shell and in some cases the plug will have been entirely removed at the time of impact with the target when the primer will be actuated as describedabove.

In the modification shown in Figure 3 a barrier ll] of flexible, fibrous material such as glass fiber, rock wool, or various other flexible fibers is aP- plied in place of a spring to maintain a rigid primer carrying slide 9 in safe position. Such a safety slide may beapplied in connection with any convenient method of primer actuation, either time or percussion, and therefore only a fragment of the projectile point'3l is shown. A radial passage ll intersects an axial bore provided in the body 31 for the primer actuating means. I Slidable in the radial passage is a'member 9 having a primer 32 or other element of firing mechanism in the section of the member normally out of alignment with the axial bore. Confined between the slide and a plug 12 closing the passage H is the barrier plug l0.

During handling and loading of the projectile the barrier ID will have suflicient elasticity to retain the slide in a position in which the primer will be protected from accidental blows.

During the initial acceleration in the bore of the gun set-back will force the slide'against the rear half of the radial passage producing sufficient frictional engagement to prevent centrifugal force from moving the slide outwardly. At the cessation of linear acceleration centrifugal force will act on the slide moving it outward against the resistance of the barrier plug, compressing the plug into a compact mass at the end of the radial passage and aligning the primer with the axial bore provided for the actuating means.

Figure lshows a portion of the .nose of a projectile embodying anothermodification of our invention. The nose of the projectile 4| is provided with an axial bore having a section of reduced diameter providing a shoulder l5 and a primer passage communicating With the interior of the shell. Secured inthe portion of reduced diameter is the primer 42. A plurality of cylindrical barriermembers M consisting of loose fibrous material such as glass fiber, rock wool, or various other flexible fibers are confined in radial bores l3 intersectin the large diameter section of the axial bore adjacent the shoulder l5. Plug members "5 or similar means may be provided to restrain the barrier members in the bores l3. Seated in the axial bore is a firing pin 43 with an enlarged head engaging the forward surfaces of the barrier members and having its point engaged between the inner ends of the barrier members. In order to prevent loss of the firing pin the nose of the cavity may be restricted by spinning or otherwise forming a flange 45 at the open end of the axial bore.

Upon firing and during handling prior thereto the barrier members being engaged between the head of the firing pin and the wide shoulder b5 provided by the restriction of the firing pin bore will exert a cushioning effect to prevent impact of the pin upon the primer. During the initial acceleration the barrier members will be pressed against the shoulder and friction will prevent their being removed from the path of the firing pin. As linear acceleration ceases the barrier members will be permitted to withdraw under the influence of centrifugal force. Upon impact the firing pin will be impelled rearwardly into contact with the primer for initiation thereof.

It will be noted that while a steady application of a force will serve to remove the fibrous barriers, accidental shocks of short duration will not be eifectiveto render the fuses unsafe.

We claim:

1. A percussion fuse comprising a fuse body, means forming an axial bore in said body, a percussion primer secured in the rear of said bore, a percussion member of less diameter than the said bore centrally supported in said bore, and a cylindrical barrier member of fibrous material secured between said primer and said percussion member, said barrier member being reduced in volume radially by centrifugal force during rotation to allow the percussion member to contact the primer.

2. A percussion fuse for projectiles comprising'a fuse body, means forming an axial firing pin bore open at the nose of said fuse body, means forming an axial primer carrying bore communicating between the firing pin bore and the inner end of the fuse'body, a percussion primer in said primer carrying bore, means forming a radial bore intersecting the firing pin bore adjacent the bottom thereof, a compressible plug'member of fibrous material secured in said radial bore and projecting into the firing pin bore in con-- tact with the bottom thereof, and a-firing pin slidably secured in said firing pin bore in advance of said plug member. v

' 3. In a fuse, amovable member having a clear.- ance from the fuse, and a barrier for said member, said barrier comprising a resilient fibrous holding member reduced in volume by centrifugal asaaeos force having an outer portion restrained against radial movement the inner portion of said holding member normally extending into the path of the movable member and adapted to be reduced in volume radially under the influence of centrifugal force to a position beyond the said clearance, thus permitting movement of the movable member.

4. In a fuse, means forming an axial bore, said bore being diametrically restricted in its rear portion to provide a shoulder and a continuation of said bore of reduced diameter, an element of firing mechanism in the reduced portion of said bore, a movable member slidable in said axial bore and having a portion of reduced diameter adapted to be projected into the said continuation of the bore, a radial bore intersecting with said axial bore adjacent the shoulder and a compressible barrier member of fibrous material in said radial bore and extending into said axial bore to be engaged between the movable member and the said shoulder.

5. In a fuse having a primer and primer firing means, a safety barrier for the protection of the primer comprising a compressible body of matted material located between the primer and the firing means, and forming the sole detent for the firing means, said fuse providing a clearance from the firing means such that the firing means will clear the detent means on radial outward compression thereof due to centrifugal force.

6. A percussion fuse comprising a fuse body, means forming an axial passageway in said body, said passageway tapering to a minimum diameter at its rearward end and open to atmosphere at its forward end, a sensitive primer seated at the rear end of said passageway and a barrier member of fibrous material having an axial opening secured in said passageway small enough to be closed by insertion of said barrier member in said tapering passageway.

JOSEPH H. CHURCH. WILFRED E. THIBODEAU. 

